Method and apparatus for generating user preference data regarding color characteristic of image and method and apparatus for converting image color preference using the method and apparatus

ABSTRACT

A method and apparatus for generating user preference data regarding the color characteristic of an image and a method and apparatus for converting image color preference using the method and apparatus is provided. The method for generating user preference data comprises (a) obtaining an image color characteristic value of a preference image and a reference image, (b) generating {preference value, reference value} which corresponds to a pair of the preference value and the reference value, and (c) generating the pair {preference value, reference value} as preference meta-data having at least one feature block. The method for converting image color preference comprises calculating a color characteristic value with respect to an input image, generating preference meta-data having at least one feature block, the feature block comprising a block header including a feature identifier corresponding to information identifying a color characteristic and at least one feature descriptor including the preference value and the reference value, obtaining a color characteristic value with respect to the input image using the calculated color characteristic value of the input image and the color preference data, and converting the color characteristic of the input image so that the input image has the obtained color characteristic value.

This application claims the priority of Korean Patent Application Nos.2002-79316 filed on Dec. 12, 2002, 2003-87993 filed on Dec. 5, 2003,respectively, in the Korean Intellectual Property Office, thedisclosures of which are incorporated herein in its entirety byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to image processing, and moreparticularly, a method and apparatus for generating user preference dataregarding the color characteristic of an image and a method andapparatus for converting image color preference using the method andapparatus.

2. Description of the Related Art

There are a variety of methods of converting images so that video has abetter color characteristic when a user views video. There are colorcharacteristics considered for conversion in the methods, such asbrightness, saturation, contrast, and color temperature. In the methods,a color characteristic value of an input image is obtained, and then,the input image is converted so that input video has a target colorcharacteristic value. However, the target color characteristic value isdetermined as desirable in each of the methods and is set collectively.Thus, in the methods, conversion which satisfies user's characteristics,cannot be performed.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus for generatinguser preference data regarding the color characteristic of an image, inwhich a conversion target value is set according to usercharacteristics.

The present invention also provides a method and apparatus forconverting image color preference using user preference data regardingthe color characteristic of an image.

The present invention also provides a recording medium on which userpreference data regarding the color characteristic of an image isrecorded.

The present invention also provides a computer readable recording mediumon which the method for generating user preference data regarding thecolor characteristic of an image and the method for converting imagecolor preference using user preference data regarding the colorcharacteristic of an image are recorded as an executable program code.

According to an aspect of the present invention, there is provided amethod for generating user preference data regarding a colorcharacteristic of an image, the method comprising (a) when an imageconverted to have a color characteristic that a user prefers withrespect to a predetermined image is referred to as a preference imageand the predetermined image is referred to as a reference image,obtaining an image color characteristic value of the preference imageand the reference image, (b) when a color characteristic value of thepreference image is referred to as a preference value and a colorcharacteristic value of the reference image is referred to as areference value, generating {preference value, reference value} whichcorresponds to a pair of the preference value and the reference value,and (c) generating the pair {preference value, reference value} aspreference meta-data having at least one feature block, and the featureblock comprises a block header including a feature identifiercorresponding to information identifying a color characteristic, and atleast one feature descriptor including the preference value and thereference value. The color characteristic may be at least one of colortemperature, brightness, contrast, and saturation. The method, beforestep (a), may further comprise providing a plurality of images havingdifferent color characteristic values with respect to a predeterminedimage, and setting an image that the user has selected from theplurality of images as a preference image, setting an original imagewith respect to the preference image as a reference image, andgenerating {preference image, reference image} which corresponds to apair of the preference image and the reference image. The method, beforestep (a), may further comprise installing a unit for controlling a colorcharacteristic of an image in an image display device, and setting animage of which color characteristic is adjusted by a user using the unitfor controlling a color characteristic, as a preference image, settingan original image of which color characteristic is not adjusted by theuser, as a reference image, and generating {preference image, referenceimage} which corresponds to a pair of the preference image and thereference image. The generating {preference image, reference image} maybe, when the reference image has a contents identifier, generating{preference image, reference image, contents identifier} whichcorresponds to a combination of the preference image, the referenceimage, and contents identifier information. Step (b) may be, when thereference image has a contents identifier and when a colorcharacteristic value of the preference image is referred to as apreference value and a color characteristic value of the reference imageis referred to as a reference value, generating {preference value,reference value, contents identifier} which corresponds to a combinationof the preference value, the reference value, and the contentsidentifier. A color temperature value in step (a) may be obtained by thefollowing steps comprising extracting a highlight region from an inputcolor image, projecting the highlight region on a chromaticitycoordinate and calculating geometric representation variables withrespect to a shape distributed on the chromaticity coordinate,estimating a color temperature from the input color image by perceptivelight source estimation, and selecting geometric representationvariables around the estimated color temperature from the geometricrepresentation variables and calculating a final color temperature usingthe selected geometric representation variables. A saturation value instep (a) may be obtained by the following steps comprising obtainingsaturation of each pixel in a HSV color space from an RGB value of apixel in the image, and generating a value obtained by adding saturationof the pixels and dividing the added saturation by the number of pixels,as a saturation value. The saturation of the pixel may be determined bythe following steps comprising obtaining maximum and minimum values ofthe RGB value of the pixel, and when the maximum value is equal to 0,setting the saturation of a corresponding pixel to 0, and when themaximum value is not equal to 0, setting a value obtained by dividing adifference between the maximum value and the minimum value by themaximum value, as the saturation of a corresponding pixel. A brightnessvalue in step (a) may be determined by the following steps comprisingobtaining luminance Y of each pixel in a YCbCr color space from an RGBvalue of a pixel in the image, and generating a value obtained by addingluminance of the pixels and dividing the added luminance by the numberof pixels, as a brightness value. The luminance Y of the pixel may bedetermined by Y=0.299×R+0.587×G+0.114×B. A contrast value CV in step (a)may be, when Y_(x) is luminance of each pixel in the image andNumberofPixels is the number of pixels in the image, determined usingequation 3:

${C\; V} = {\sqrt{\frac{\lbrack {\cdot {\sum\limits_{x \in {({pixels})}}\; ( {Y_{x} - {BV}} )^{2}}} \rbrack}{NumberOfPixels}}.}$

Step (b) may further comprise, when {preference value, reference value}exists before {preference value, reference value} in step (b) isgenerated, comparing the pair {preference value, reference value}generated in step (b) with an existing pair {preference value, referencevalue} and updating the pair {preference value, reference value}, andthe updating is, with respect to one preference value, when thereference value generated in step (b) is compared with the existingreference value and is the same as or similar to the existing referencevalue, removing the existing reference value. The updating may be, whenquantization levels of the two reference values are different,converting a value of high level into a value of low level and comparingwith each other, and when image contents identifiers are added to thecharacteristic value pairs, even though the two reference values are thesame as or similar to each other, if the image contents identifiers aredifferent, without removing the existing reference value.

The number of the feature blocks may be four, and each of the featureblocks may correspond to the four characteristic values. The blockheader of the feature block may represent color temperature if the valueof the feature identifier is ‘0’, brightness if the value thereof is‘1’, contrast if the value thereof is ‘2’, and saturation if the valuethereof is ‘3’. The block header of the feature block may furthercomprise a number-of-descriptors value indicating the number of featuredescriptors contained in the feature block. The feature descriptor mayfurther comprise a Bin number indicating a quantization level of thecharacteristic value, a contents ID flag indicating the presence of animage contents identifier, and a contents identifier if the imagecontents identifier exists.

According to another aspect of the present invention, there is providedan apparatus for generating user preference data regarding a colorcharacteristic of an image, the apparatus comprising a colorcharacteristic calculating unit, which, when an image converted to havea color characteristic that a user prefers with respect to apredetermined image is referred to as a preference image and thepredetermined image is referred to as a reference image, obtains animage color characteristic value of the preference image and thereference image, and when a color characteristic value of the preferenceimage is referred to as a preference value and a color characteristicvalue of the reference image is referred to as a reference value,generates {preference value, reference value} which corresponds to apair of the preference value and the reference value, and a meta-datagenerating unit, which generates the pair {preference value, referencevalue} generated in the color characteristic calculating unit aspreference meta-data having at least one feature block, and the featureblock comprises

a block header including a feature identifier corresponding toinformation identifying a color characteristic, and at least one featuredescriptor including the preference value and the reference value.

The apparatus may further comprise a first sample image obtaining unit,which sets an image that the user has selected from a plurality ofimages having different color characteristic values with respect to apredetermined image, sets an original image with respect to thepreference image as a reference image, generates {preference image,reference image} which corresponds to a pair of the preference image andthe reference image, and outputs the pair to the color characteristiccalculating unit.

The apparatus may further comprise a second sample image obtaining unit,which, when a unit for controlling a color characteristic of an image isinstalled in an image display device, sets an image of which colorcharacteristic is adjusted by a user using the unit for controlling acolor characteristic, as a preference image, sets an original image ofwhich color characteristic is not adjusted by the user, as a referenceimage, generates {preference image, reference image} which correspondsto a pair of the preference image and the reference image, and outputsthe pair to the color characteristic calculating unit. The generating{preference image, reference image} may be, when the reference image hasa contents identifier, generating {preference image, reference image,contents identifier} which corresponds to a combination of thepreference image, the reference image, and contents identifierinformation.

The color characteristic calculating unit, when the reference image hasa contents identifier, may further comprise a contents identifier in thepair {preference value, reference value} and may generate a combination{preference value, reference value, contents identifier}. The colorcharacteristic calculating unit comprises a color temperature valuecalculating portion, which obtains a color temperature value, and thecolor temperature value calculating portion comprises a highlightdetecting part, which extracts a highlight region from an input colorimage, a highlight variable calculating part, which projects thehighlight region on a chromaticity coordinate and calculates geometricrepresentation variables with respect to a shape distributed on thechromaticity coordinate, a color temperature estimating part, whichestimates a color temperature from the input color image by perceptivelight source estimation, and a color temperature calculating part, whichselects geometric representation variables around the estimated colortemperature from the geometric representation variables and calculates afinal color temperature using the selected geometric representationvariables. The color characteristic calculating unit comprises asaturation value calculating portion, which obtains saturation of eachpixel in a HSV color space from an RGB value of a pixel in the image andgenerates a value obtained by adding saturation of the pixels anddividing the added saturation by the number of pixels, as a saturationvalue, and the saturation of the pixel is determined by the followingsteps comprising obtaining maximum and minimum values of the RGB valueof the pixel, and when the maximum value is equal to 0, setting thesaturation of a corresponding pixel to 0, and when the maximum value isnot equal to 0, setting a value obtained by dividing a differencebetween the maximum value and the minimum value by the maximum value, asthe saturation of a corresponding pixel. The color characteristiccalculating unit comprises a brightness value calculating portion, whichobtains luminance Y of each pixel in a YCbCr color space from an RGBvalue of a pixel in the image and generates a value obtained by addingluminance of the pixels and dividing the added luminance by the numberof pixels, as a brightness value, and the luminance Y of the pixel isdetermined by Y=0.299×R+0.587×G+0.114×B. The color characteristiccalculating unit comprises a contrast value calculating portion, which,when Y_(x) is luminance of each pixel in the image and NumberofPixels isthe number of pixels in the image, calculates a contrast valuedetermined using equation 3:

${C\; V} = {\sqrt{\frac{\lbrack {\sum\limits_{x \in {({pixels})}}\; ( {Y_{x} - {BV}} )^{2}} \rbrack}{NumberOfPixels}}.}$

The apparatus may further comprise a meta-data updating unit, whichcompares the pair {preference value, reference value} generated in thecolor characteristic calculating unit with an existing pair {preferencevalue, reference value}, updates the pair {preference value, referencevalue}, and outputs the pair to the meta-data generating unit, and theupdating may be, with respect to one preference value, when thereference value generated in step (b) is compared with the existingreference value and is the same as or similar to the existing referencevalue, removing the existing reference value, and the updating is, whenquantization levels of the two reference values are different,converting a value of high level into a value of low level and comparingwith each other, and when image contents identifiers are added to thecharacteristic value pairs, even though the two reference values are thesame as or similar to each other, if the image contents identifiers aredifferent, without removing the existing reference value.

The block header of the feature block may further comprise the number ofdescriptor indicating the number of feature descriptors contained in thefeature block. The feature descriptor may further comprise a Bin numberindicating a quantization level of the characteristic value, a contentsID flag indicating the presence of an image contents identifier, and acontents identifier if the image contents identifier exists.

According to another aspect of the present invention, there is providedan apparatus for converting image color preference, the apparatuscomprising an input image color characteristic calculating unit, whichcalculates a color characteristic value with respect to an input image,a color preference data unit, which generates preference meta-datahaving at least one feature block, the feature block comprising a blockheader including a feature identifier corresponding to informationidentifying a color characteristic and at least one feature descriptorincluding the preference value and the reference value, an image colorcharacteristic mapping unit, which determines a target colorcharacteristic value with respect to the input image using the colorcharacteristic value of the input image calculated by the input imagecolor characteristic calculating unit and the color preference dataoutput from the color preference data unit, and an image colorcharacteristic converting unit, which converts the color characteristicof the input image so that the input image has a color characteristicvalue obtained from the image color characteristic mapping unit. Theblock header of the feature block of the color preference data unit mayfurther comprise a number-of-descriptors value indicating the number offeature descriptors contained in the feature block, and the featuredescriptor of the color preference data unit may further comprise a Binnumber indicating a quantization level of the characteristic value, acontents ID flag indicating the presence of an image contentsidentifier, and a contents identifier if the image contents identifierexists.

When a contents identifier of the input image exists, the image colorcharacteristic mapping unit may determine a target color characteristicvalue with respect to the input image using the color characteristicvalue of the input image calculated by the input image colorcharacteristic calculating unit and a color characteristic value of samecontents identifier stored in the color preference data unit. The imagecolor characteristic converting unit may comprise a color temperatureconverting portion, which converts the input image so that the inputimage has a color temperature value generated in the image colorcharacteristic mapping unit, a brightness converting portion, whichconverts the input image so that the input image has a brightness valuegenerated in the image color characteristic mapping unit, a contrastconverting portion, which converts the input image so that the inputimage has a contrast value generated inn the image color characteristicmapping unit, and a saturation converting portion, which converts theinput image so that the input image has a saturation value generated inthe image color characteristic mapping unit.

According to another aspect of the present invention, there is provideda method for converting image color preference, the method comprising(a) calculating a color characteristic value with respect to an inputimage, (b) generating preference meta-data having at least one featureblock, the feature block comprising a block header including a featureidentifier corresponding to information identifying a colorcharacteristic and at least one feature descriptor including thepreference value and the reference value, (c) determining a target colorcharacteristic value with respect to the input image using the colorcharacteristic value of the input image calculated in step (a) and thecolor preference data output in step (b), and (d) converting the colorcharacteristic of the input image so that the input image has the colorcharacteristic value obtained in step (c). The block header of thefeature block of the color preference data unit may further comprise anumber-of-descriptors value indicating the number of feature descriptorscontained in the feature block, and the feature descriptor in step (b)may further comprise a Bin number indicating a quantization level of thecharacteristic value, a contents ID flag indicating the presence of animage contents identifier, and a contents identifier if the imagecontents identifier exists. In step (c), when a contents identifier ofthe input image exists, a color characteristic value with respect to theinput image may be obtained using the color characteristic value of theinput image calculated in step (a) and a color characteristic value ofsame contents identifier output in step (b).

According to another aspect of the present invention, there is providedan image preference data recording medium on which, when an imageconverted to have a color characteristic that a user prefers withrespect to a predetermined image is referred to as a preference image,the predetermined image is referred to as a reference image, a colorcharacteristic value of the preference image is referred to as apreference value, and a color characteristic value of the referenceimage is referred to as a reference value, preference meta-data havingat least one feature block, the feature block comprising a block headerincluding a feature identifier corresponding to information identifyinga color characteristic and at least one feature descriptor including thepreference value and the reference value is recorded. The block headerof the feature block may further comprise a number-of-descriptors valueindicating the number of feature descriptors contained in the featureblock, and the feature descriptor may further comprise a Bin numberindicating a quantization level of the characteristic value, a contentsID flag indicating the presence of an image contents identifier, and acontents identifier if the image contents identifier exists.

There is provided a computer readable recording medium on which theinvention is recorded as an executable program code.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and advantages of the present invention willbecome more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a block diagram illustrating a structure of an apparatus forgenerating user preference data regarding the color characteristic of animage according to the present invention;

FIG. 2 is a block diagram illustrating a structure of a sample imageobtaining unit;

FIG. 3 is a block diagram illustrating a structure of a colorcharacteristic calculating unit;

FIG. 4 is a block diagram illustrating a structure of a colortemperature value calculating portion;

FIG. 5 illustrates a structure of preference meta-data according to thepresent invention;

FIG. 6 is a flowchart illustrating a method for generating userpreference data regarding the color characteristic of an image accordingto the present invention;

FIG. 7 is a block diagram illustrating a structure of an apparatus forconverting image color preference using preference data regarding thecolor characteristic of an image according to the present invention;

FIG. 8 is a block diagram illustrating a structure of an image colorcharacteristic converting unit; and

FIG. 9 is a flowchart illustrating a method for converting image colorpreference using user preference data regarding the color characteristicof an image according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a method and apparatus for generating user preference dataregarding the color characteristic of an image and a method andapparatus for converting image color preference using user preferencedata regarding the color characteristic of an image according to thepresent invention will be described in detail with reference to theaccompanying drawings.

First, a method and apparatus for generating user preference dataregarding the color characteristic of an image according to the presentinvention will be described as below.

FIG. 1 is a block diagram illustrating a structure of an apparatus forgenerating user preference data regarding the color characteristic of animage according to the present invention. The apparatus for generatinguser preference data regarding the color characteristic of an imageaccording to the present invention includes a preference obtainer 100and a preference data generator 150. FIG. 6 is a flowchart illustratinga method for generating user preference data regarding the colorcharacteristic of an image according to the present invention. Themethod for generating user preference data regarding the colorcharacteristic of an image according to the present invention comprisesobtaining a sample image (step 600), calculating a color characteristicvalue (step 620), updating meta-data (step 640), and generatingpreference meta-data (step 660).

First, terms used in the present invention will be described. An imageconverted to have a color characteristic that a user prefers withrespect to a predetermined image is referred to as a preference image,and the predetermined image is referred to as a reference image. Inaddition, a color characteristic value of the preference image isreferred to as a preference value, and a color characteristic value ofthe reference image is referred to as a reference value.

Preferably, a color characteristic considered in the present inventionincludes at least one of color temperature, brightness, contrast, andsaturation. All of the color temperature, the brightness, the contrast,and the saturation are applied to a general case to which the presentinvention is applied. In addition, the color characteristic consideredin the present invention is not limited to the four colorcharacteristics, but other color characteristics may be considered inthe present invention.

The preference obtainer 100 obtains a preference image and a referenceimage from a predetermined image, generates a preference value and areference value from the obtained preference image and the referenceimage, respectively, and includes a sample image obtaining unit 10 and acolor characteristic calculating unit 12.

FIG. 2 is a block diagram illustrating a structure of the sample imageobtaining unit 10. The sample image obtaining unit 10 generates a pairof a preference image and a reference image, from a user's selection ora user's color adjustment (step 600). There are two methods forgenerating the pair of the preference image and the reference image. Themethods correspond to a first sample image obtaining portion 200 and asecond sample image obtaining portion 250 shown in FIG. 2, respectively.Thus, the present embodiment, the sample image obtaining unit 10includes at least one of the first sample image obtaining portion 200and the second sample image obtaining portion 250.

The first sample image obtaining portion 200 sets an image that the userhas selected from a plurality of images having different colorcharacteristic values with respect to a predetermined image as apreference image, sets an original image with respect to the preferenceimage as a reference image, generates {preference image, referenceimage} which corresponds to a pair of the preference image and thereference image, and outputs the pair to the color characteristiccalculating unit 12. In other words, the first sample image obtainingportion 200 constitutes a set of images converted to have differentcharacteristic values from an original image with respect to each offour characteristics, such as color temperature, brightness, contrast,and saturation. Then, the first sample image obtaining portion 200 setsan image that the user has preferred, as a preference image, sets theoriginal images as a reference image, and sets a pair {preference image,reference image}.

When a unit (not shown) for controlling a color characteristic of animage is installed in an image display device, the second sample imageobtaining part 250 sets an image of which color characteristic isadjusted by the user using the unit for controlling a colorcharacteristic, as a preference image, sets an original image of whichcolor characteristic is not adjusted by the user, as a reference image,generates {preference image, reference image} which corresponds to apair of the preference image and the reference image, and outputs thepair to the color characteristic calculating unit 12. In other words,when the unit for controlling a color characteristic of an image isinstalled in the image display device, the user adjusts a colorcharacteristic using the unit when viewing video. In this case, theimage before the user adjusts is referred to as a reference image, andthe image obtained after the user has adjusted is referred to as apreference image.

When image contents including the reference image obtained by the firstsample image obtaining portion 200 and the second sample image obtainingportion 250 have a contents identifier set by MPEG-21, TV anytime, orcontents service provider, the sample image obtaining unit 10 can outputan image contents identifier as well as the pair {preference image,reference image}.

The color characteristic calculating unit 12 calculates colorcharacteristic values of the preference image and the reference image,generates a pair {preference value, reference value} which correspondsto a pair of a preference value and a reference value, and includes atleast one of a color temperature value calculating portion 300, asaturation value calculating portion 320, a brightness value calculatingportion 340, and a contrast value calculating portion 360.

More specifically, the color characteristic calculating unit 12calculates all or a part of a color temperature value, a brightnessvalue, a contrast value, and a saturation value with respect to an inputpair {preference image, reference image} and outputs a pair {preferencevalue, reference value} (step 620). When the color temperaturecalculating unit 12 receives an image contents identifier together withthe pair {preference image, reference image}, the color temperaturecalculating unit 12 outputs the image contents identifier together withthe pair {preference value, reference value}. The color characteristiccalculating unit 12 calculates each color characteristic of an inputimage by the following method.

FIG. 4 is a block diagram illustrating a structure of the colortemperature value calculating portion 300. The color temperature valuecalculating portion 300 calculates a color temperature value from aninput color image and includes a highlight detecting part 400, ahighlight variable calculating part 420, a color temperature estimatingpart 440, and a color temperature calculating part 460. The highlightdetecting part 400 extracts highlight regions from the input colorimage. The highlight variable calculating part 420 projects thehighlight regions on a chromaticity coordinate and calculates geometricrepresentation variables with respect to a shape distributed on thechromaticity coordinate. The color temperature estimating part 440estimates a color temperature from the input color image by perceptivelight source estimation. The color temperature calculating part 460selects geometric representation variables around the estimated colortemperature from the geometric representation variables and calculates afinal color temperature using the selected geometric representationvariables. The color temperature value may be expressed as 8-bit data,as specified in a color temperature descriptor ISO/IEC 15938-3.

The saturation value calculating portion 320 obtains saturationcorresponding to S in a HSV color space of each pixel from an RGB valueof a pixel in an image to be displayed and generates a value obtained byadding saturation of the pixels and dividing the added saturation by thenumber of pixels, as a saturation value. When maximum and minimum valuesof the RGB value of the pixel are obtained and the maximum value isequal to 0, the saturation of a corresponding pixel is set to 0, andwhen the maximum value is not equal to 0, a value obtained by dividing adifference between the maximum value and the minimum value by themaximum value, is set as the saturation of a corresponding pixel.

This will be expressed using the following equation. Saturation S in theHSV color space is obtained from (R,G,B) values of each pixel in aninput image as below.

Max=max(R,G,B),

Min=min(R,G,B)

if(Max==0) S=0 else S=(Max−Min)/Max

A saturation value SV is calculated using equation 1.

$\begin{matrix}{{S\; V} = \frac{\lbrack {\sum\limits_{x \in {({pixels})}}\; S_{x}} \rbrack}{NumberOfPixels}} & (1)\end{matrix}$

Here, S_(x) is an S-value of each pixel in an image to be displayed.

The brightness value calculating portion 340 obtains luminance Ycorresponding to Y in a YCbCr color space of each pixel from an RGBvalue of a pixel in an image to be displayed and generates a valueobtained by adding luminance of the pixels and dividing the addedluminance by the number of pixels, as a brightness value. The luminanceY of the pixel is determined by Y=0.299×R++0.587×G+0.114×B.

A brightness value BV is calculated using equation 2.

$\begin{matrix}{{B\; V} = \frac{\lbrack {\sum\limits_{x \in {({pixels})}}\; Y_{x}} \rbrack}{NumberOfPixels}} & (2)\end{matrix}$

Here, Y_(x) is a Y-value of each pixel in an image to be displayed.

When Y_(x) is luminance of each pixel in the image, NumberofPixels isthe number of pixels in the image and a contrast value is CV, thecontrast value calculating portion 360 calculates the contrast value CVusing equation 3.

$\begin{matrix}{{C\; V} = \sqrt{\frac{\lbrack {\sum\limits_{x \in {({pixels})}}\; ( {Y_{x} - {BV}} )^{2}} \rbrack}{NumberOfPixels}}} & (3)\end{matrix}$

The preference obtainer 100 may include only the color characteristiccalculating unit 12 without the sample image obtaining unit 10 when apreference image and a reference image are previously prepared.

Meanwhile, the preference data generator 150 receives the preferencevalue and the reference value generated in the preference obtainer 100,generates preference meta-data having at least one feature block, andincludes a meta-data updating unit 16 and a metal-data generating unit18.

The meta-data updating unit 16 compares the pair {preference value,reference value} generated in the color characteristic calculating unit12 with an existing pair {preference value, reference value}, updatesand outputs the pair {preference value, reference value} to themeta-data generating unit 18 (step 640).

The meta-data updating unit 16 operates when preference meta-dataalready exists. The meta-data updating unit 16 receives a pair or aplurality of pairs {preference value, reference value} from thepreference obtainer 100. In addition, the meta-data updating unit 16receives characteristic value pairs in existing preference meta-data,removes redundancy and contradiction of the preference data, and then,outputs updated pairs {preference value, reference value}. The meta-dataupdating unit 16 operates with respect to each preference as below.

When with respect to one preference, a newly-input characteristic valuepair is A and an existing characteristic value pair is B, a referencevalue of A is compared with a reference value of B. When the referencevalue of A is the same as or similar to the reference value of B, B isremoved. Here, a similar case means a case where a difference betweenthe reference value of A and the reference value of B is within apredetermined range. In addition, when quantization levels of the tworeference values are different, a value of high level is converted intoa value of low level and is compared with each other.

When image contents identifiers are added to the characteristic valuepairs, even though the reference value of A is the same as or similar tothe reference value of B, if the image contents identifiers aredifferent, B is not removed. The existing characteristic value pairs andthe new characteristic value pairs, which are not removed in the aboveprocedure, are output.

The meta-data generating unit 18 receives the pair {preference value,reference value} from the meta-data updating unit 16 or the colorcharacteristic calculating unit 12 and generates preference meta-datahaving at least one feature block (step 660). The feature block includesa block header including a feature identifier corresponding toinformation identifying a color characteristic and at least one featuredescriptor including the preference value and the reference value.

The preference meta-data will be described in more detail as below. Whena contents identifier is input, identifier information is added tometa-data, as shown in FIG. 5.

The preference meta-data is composed of four feature blocks 500, 505,510, and 515. Each of the four feature blocks 500, 505, 510, and 515 hasinformation corresponding to each of four preferences, such as colortemperature, saturation, brightness, and contrast.

Each feature block includes one block header 520 and a plurality offeature descriptors 525, 530, . . . , and 535 or one thereof. The blockheader 520 includes a feature identifier 540 indicating that a colorcharacteristic to be represented, and a number-of-descriptors value 545indicating how many feature descriptors exist in a corresponding block.If the above data structure is represented in a binary sequence, thefeature identifier 540 may be represented with a 2-bit flag. In thiscase, if the value of the feature identifier 540 is ‘0’, the featureidentifier 540 may be represented with color temperature. If the valuethereof is ‘1’, the feature identifier 540 may be represented withbrightness. If the value thereof is ‘2’, the feature identifier 540 maybe represented with contrast, and if the value thereof is ‘3’, thefeature identifier 540 may be represented with saturation. In addition,the number-of-descriptors value 545 may be represented with a variableflag indicating that, for example, 3 bits of 4 bits mean the number ofbits and if last 1 bit is 1, 4 bits continue.

If the above data structure is represented with XML, the featureidentifier 540 is represented with a string, and thenumber-of-descriptors value 545 is not represented.

The feature descriptor 530 includes a Bin number 550 indicating aquantization level of the characteristic value, a contents ID flag 555indicating the presence of an image contents identifier, a contentsidentifier 560, a preference value 565, and a reference value 570.

The Bin number indicates the quantization level of characteristic valuerepresentation. The quantization level of the characteristic value iswithin a range of 8 bits with respect to color temperature and is withina range of 12 bits with respect to other characteristic values.

If the data structure is represented with XML, the contents ID flag isnot represented. The above-described color preference data may berepresented/recorded as xml-data according to xml-schema definition.

A data format generated in the meta-data generating unit may berepresented as xml-data according to xml-schema definition.

1. DisplayPresentationPreferences

DisplayPresentationPreferences specifies the preferences of a userregarding the display of images and video.

1.1 DisplayPresentationPreferences syntax <!--################################################ --> <!--  Definition ofDisplayPresentationPreferences  --> <!--################################################ --> <complexTypename=“DisplayPresentationPreferencesType”>   <complexContent>    <extension base=“dia:DIABaseType”>       <sequence>         <elementname=“ColorTemperaturePreference”         type=“dia:ColorPreferenceType”           minOccurs=“0”/>          <element name = “BrightnessPreference”            type =“dia:ColorPreferenceType”           minOccurs=“0”/>          <elementname=“SaturationPreference”            type=“dia:ColorPreferenceType”          minOccurs=“0”/>         <element name=“ContrastPreference”           type = “dia:ColorPreferenceType”           minOccurs=“0”/>      </sequence>     </extension>   </complexContent> </complexType>

1.2 DisplayPresentationPreferences Semantics

DisplayPresentationPreferencesType is a tool that describes the displaypresentation preferences of a user.

ColorTemperaturePreference describes the color temperature that a Userprefers. The color temperature is defined as the correlated colortemperature of estimated illumination of the image to be displayed.

BrightnessPreference describes the brightness that a user prefers. Thebrightness is defined as an attribute of a visual sensation according towhich an area appears to emit more or less light.

SaturationPreference describes the saturation that a user prefers. Thesaturation is defined as the colorfulness of an area judged inproportion to its brightness.

ContrastPreference describes the contrast that a user prefers. Thecontrast is defined to be the ratio of luminance between the lightestand darkest elements of a scene.

StereoscopicVideoConversion describes the preferred parameters of a userfor stereoscopic video conversion.

2. ColorPreference

ColorPreference specifies color preference. InDisplayPresentationPreference, to express a users preference regardingthe color of displayed image and video, four attributes of color areconsidered; color temperature, brightness, saturation and contrast. TheColorPreferenceType is a tool to describe preferences related to suchattributes of color.

2.1 ColorPreference syntax   <!--############################################### -->   <!-- Definition ofColorPreference       -->   <!--################################################ -->   <complexTypename=“ColorPreferenceType”>    <complexContent>     <extensionbase=“dia:DIABaseType”>      <sequence>        <element name=“BinNumber”type=“mpeg7:        unsigned12”/>       <element name=“Value”minOccurs=“0”       maxOccurs=“unbounded”>        <complexType>       <sequence>         <element name = “PreferredValue”        type=“mpeg7:unsigned12”/>         <element name =“ReferenceValue” type=“mpeg7:unsigned12”/>        </sequence>        </complexType>       </element>      </sequence>    </extension>    </complexContent>   </complexType>

2.2 ColorPreference Sematics

ColorPreferenceType is a tool that describes the color preferences of auser when viewing visual images. The color preference can be describedin terms of color temperature, brightness, saturation and contrast.

BinNumber describes the quantization level that PreferredValue andReferenceValue take.

Value Indicates the minimal unit that describes the color preference ofa user. It includes two subelements: PreferredValue and ReferenceValue.If PreferredValue is equal to v1, and ReferenceValue is equal to v2, itindicates that the user wants to convert an image of value v2 into animage of value v1 with respect to an attribute of color thatColorPreferenceType descriptor specifies.

PreferredValue describes the value of a color attribute that a userprefers.

ReferenceValue describes the value of a color attribute in an image thatis used as reference to express the PreferredValue. If ReferenceValue isequal to zero, it means that ReferenceValue is not considered.

Table 1 gives the value definition of PreferredValue and ReferenceValuefor four attributes of color: color temperature, brightness, saturationand contrast of images and videos to be displayed.

TABLE 1 Value Range, Number of Attribute Name Value Type ValueDefinition Bins, Quantization Type Color Temperature Color Temperatureis Correlated color temperature of The range [1667, 25000] is specifiedin ISO/IEC estimated illumination of the quantized into 2⁸ bins in a15938-3 image to be displayed non-uniform way as specified in ISO/IEC15938-3 Brightness Y-value in the YCbCr* Mean value of Y-values of allThe range [0, 1] is uniformly color space pixels in the image to bequantized. Number of bins ≦ 2¹². displayed Saturation S-value in theHSV* Mean value of S-values of all The range [0, 1] is uniformly colorspace pixels in the image to be quantized. Number of bins ≦ 2¹².displayed Contrast Y-value in the YCbCr* Standard deviation of Y-valuesThe range [0, 1] is uniformly color space of all pixels in the image tobe quantized. Number of bins ≦ 2¹². displayed

In Table 1, the color spaces YCbCr and HSV are specified in ISO/IEC15938-3. The standard expressions of Y value and S value are alsospecified there.

2.3 ColorPreference Examples

ColorPreference allows multiple occurrences of the pair,(PreferredValue,ReferenceValue) so that the pairs can be used to find anoptimal mapping of color attributes, for example, through selectionamong available mapping functions or interpolation by using the pairs aspoles. Based on the obtained mapping strategy, an application mayconvert images so that the resulting images satisfy the user preferencefor color. The following example shows the use of theDisplayPresentationPreferences description tool to express colorpreference of user.

<DIA>  <Description xsi:type=“UsageEnvironmentType”>   <UsageEnvironmentxsi:type=“UserCharacteristicsType”>    <UserCharacteristicsxsi:type=“PresentationPreferencesType”>     <Display>     <ColorTemperaturePreference>       <BinNumber>255</BinNumber>      <Value>        <PreferredValue>110</PreferredValue>       <ReferenceValue>127</ReferenceValue>       </Value>       <Value>       <PreferredValue>156</PreferredValue>       <ReferenceValue>151</ReferenceValue>       </Value>       <Value>       <PreferredValue>200</PreferredValue>       <ReferenceValue>192</ReferenceValue>       </Value>     </ColorTemperaturePreference>      <BrightnessPreference>       <BinNumber>255</BinNumber>       <Value>       <PreferredValue>138</PreferredValue>       <ReferenceValue>103</ReferenceValue>       </Value>       <Value>       <PreferredValue>152</PreferredValue>       <ReferenceValue>150</ReferenceValue>       </Value>     </BrightnessPreference>      <SaturationPreference>       <BinNumber>255</BinNumber>       <Value>       <PreferredValue>94</PreferredValue>       <ReferenceValue>80</ReferenceValue>       </Value>     </SaturationPreference>      <ContrastPreference>       <BinNumber>255</BinNumber>        <Value>       <PreferredValue>80</PreferredValue>       <ReferenceValue>70</ReferenceValue>       </Value>     </ContrastPreference>     </Display>    </UserCharacteristics>  </UsageEnvironment>  </Description> </DIA>

Next, a method and apparatus for converting image color preference usinguser preference data regarding the color characteristic of an imageaccording to the present invention will be described in detail.

FIG. 7 is a block diagram illustrating a structure of an apparatus forconverting image color preference using preference data regarding thecolor characteristic of an image according to the present invention. Theapparatus for converting image color preference includes an input imagecolor characteristic calculating unit 700, a color preference data unit720, an image color characteristic mapping unit 740, and an image colorcharacteristic converting unit 760. FIG. 9 is a flowchart illustrating amethod for converting image color preference using user preference dataregarding the color characteristic of an image according to the presentinvention. The method for converting image color preference comprisescalculating an input image color characteristic value (step 900),generating and providing user preference meta-data (step 920),generating a target color characteristic value from the input imagecolor characteristic value and the user preference meta-data (step 940),and converting a color characteristic of an input image (step 960).

The input image color characteristic calculating unit 700 calculates acolor characteristic value with respect to an input image (step 900).The input image color characteristic calculating unit 700 calculates atleast one of four color characteristics, such as color temperature,saturation, brightness, and contrast, from the input image. The colorcharacteristic value may be calculated by the color temperature valuecalculating portion 300, the saturation value calculating portion 320,the brightness value calculating portion 340, and the contrast valuecalculating portion 360 of the color characteristic calculating unit 12shown in FIG. 3. The calculated color characteristic value is recordedin each frame of an image or in each image time period, and thus, aninput image color characteristic is output.

The color preference data unit 720 generates preference meta-data havingat least one feature block and provides the preference meta-data to theimage color characteristic mapping unit 740 (step 920). The colorpreference data unit 720 is the same as the apparatus for generatinguser preference data regarding the color characteristic of an image ofFIG. 1.

The image color characteristic mapping unit 740 determines a targetcolor characteristic value with respect to the input image using thecolor characteristic value of the input image calculated by the inputimage color characteristic calculating unit 700 and the color preferencedata output from the color preference data unit 720 (step 940).

More specifically, input image color characteristic data is input intothe image color characteristic mapping unit 740, and then, the imagecolor characteristic mapping unit 740 receives color preference datahaving a reference value being equal to or approximating the input imagecolor characteristic value from the color preference data unit 720. If acontents identifier is contained in an input image, the image colorcharacteristic mapping unit 740 may receive color preference datacomposed of a combination {preference value, reference value, imagecontents identifier} having same contents identifier from the colorpreference data unit 720. As a result, the image color characteristicmapping unit 740 determines and outputs a target color characteristicvalue using the input image color characteristic value and the colorpreference data.

The image color characteristic converting unit 760 converts the colorcharacteristic of the input image so that the input image has a targetcolor characteristic value determined using the image colorcharacteristic mapping unit 740 (step 960). FIG. 8 is a block diagramillustrating a structure of the image color characteristic convertingunit 760. The image color characteristic converting unit 760 includesthe a color temperature converting portion 800, a brightness convertingportion 820, a contrast converting portion 840, and a saturationconverting portion 860.

The color temperature converting portion 800 converts the input image sothat the input image has a target color temperature value determined bythe image color characteristic mapping unit 740. Color temperatureconversion may be performed diversely. An example of color temperatureconversion is as follows: an input color temperature of an input imageis estimated. The estimated color temperature of the input image and auser preference color temperature are received. When a predeterminedreference color temperature is converted into the user preference colortemperature by a predetermined mapping method, a target colortemperature of an output image in which the color temperature of theinput image is converted by the mapping method is obtained. Then, acolor temperature conversion coefficient is obtained using the inputcolor temperature and the output color temperature, and the input imageis converted into an output image having the target color temperaturebased on the color temperature conversion coefficient.

The brightness converting portion 820 converts the input image so thatthe input image has a brightness value generated in the image colorcharacteristic mapping unit 740. Brightness conversion of an image maybe performed diversely. An example of image brightness conversion is asfollows: first, a brightness enhancement reference value of apredetermined pixel is obtained. A brightness enhancement ratio isobtained by dividing the brightness enhancement reference value by amaximum component value. Then, brightness is enhanced by multiplyingeach component of the predetermined pixel by the brightness enhancementratio.

The contrast converting portion 840 converts the input image so that theinput image has a contrast value generated inn the image colorcharacteristic mapping unit 740. Contrast conversion of an image may beperformed diversely. An example of image contrast conversion is asfollows: first, average brightness in one frame of an image is obtained.A brightness enhancement parameter is calculated from the averagebrightness of the image. Maximum and minimum values of the brightnessrange of the image are calculated. An application brightness rangemaximum value/minimum value is calculated. Brightness range extension iscalculated in each pixel and in each section. Brightness enhancementvalues are calculated in each pixel using the brightness enhancementparameter. Calculation of brightness range extension in each pixel andin each section and calculation of brightness enhancement values in eachpixel using the brightness enhancement parameter are repeatedlyperformed until all pixels in one frame of the image are processed.

The saturation converting portion 860 converts the input image so thatthe input image has a saturation value generated in the image colorcharacteristic mapping unit 740. Saturation conversion of an image maybe performed diversely. An example of image saturation conversion is asfollows: first, a saturation component is extracted from an input image.A saturation enhancement function used to enhance saturation of theinput image is determined according to a predetermined reference value.Then, the extracted saturation component is changed using the saturationenhancement function, the changed saturation component and the remainingcomponent of the input image are synthesized, thereby generating anoutput color value. An output image is generated based on the outputcolor value.

The present invention can also be embodied on computer (including alldevices having an information processing function) readable recordingmedia. The computer readable recording media include all types ofrecording devices in which data that can be read by a computer systemare stored, such as ROMs, RAMs, CD-ROMs, magnetic tapes, floppy discs,and optical data storage units.

As described above, in a method and apparatus for generating userpreference data regarding the color characteristic of an image and amethod and apparatus for converting image color preference using themethod and apparatus, a target value that satisfies user'scharacteristics is set when a color characteristic of an image isconverted, such that a converted image that satisfies user preferencecan be obtained.

In addition, since a color preference data structure generated accordingto the present invention can be represented with a data format, such asXML and binary sequence, the color preference data structure can becommonly used to generate video that satisfies user preference in animage display device having a variety of obtained color preferences,image display software, and a service system and apparatus for supplyingvideo to a user via wire/wireless transmission.

While this invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

1. A method for generating user preference data regarding a colorcharacteristic of an image, when an image converted to have a colorcharacteristic that a user prefers with respect to a predeterminedreference image is referred to as a preference image, a colorcharacteristic value of the preference image is referred to as apreference value and a color characteristic value of the reference imageis referred to as a reference value, the method comprising: (a)generating {preference value, reference value} which corresponds to apair of the preference value and the reference value; and (b) generatingthe pair {preference value, reference value} as preference meta-datahaving at least one feature block, wherein the feature block comprises:a block header including a feature identifier corresponding toinformation identifying a color characteristic; and at least one featuredescriptor including the preference value and the reference value. 2.The method of claim 1, wherein the color characteristic is at least oneof color temperature, brightness, contrast, and saturation.
 3. Themethod of claim 2, before step (a), further comprising: providing aplurality of images having different color characteristic values withrespect to a predetermined image; and setting an image that the user hasselected from the plurality of images as a preference image, setting anoriginal image with respect to the preference image as a referenceimage, and generating {preference image, reference image} whichcorresponds to a pair of the preference image and the reference image.4. The method of claim 2, before step (a), further comprising:installing a unit for controlling a color characteristic of an image inan image display device; and setting an image of which colorcharacteristic is adjusted by a user using the unit for controlling acolor characteristic, as a preference image, setting an original imageof which color characteristic is not adjusted by the user, as areference image, and generating {preference image, reference image}which corresponds to a pair of the preference image and the referenceimage.
 5. The method of claim 3, wherein the generating {preferenceimage, reference image} is, when the reference image has a contentsidentifier, generating {preference image, reference image, contentsidentifier} which corresponds to a combination of the preference image,the reference image, and contents identifier information.
 6. The methodof claim 4, wherein the generating {preference image, reference image}is, when the reference image has a contents identifier, generating{preference image, reference image, contents identifier} whichcorresponds to a combination of the preference image, the referenceimage, and contents identifier information.
 7. The method of claim 2,wherein step (a) is, when the reference image has a contents identifierand when a color characteristic value of the preference image isreferred to as a preference value and a color characteristic value ofthe reference image is referred to as a reference value, generating{preference value, reference value, contents identifier} whichcorresponds to a combination of the preference value, the referencevalue, and the contents identifier.
 8. The method of claim 2, wherein acolor temperature value is obtained by the following steps comprising:extracting a highlight region from an input color image; projecting thehighlight region on a chromaticity coordinate and calculating geometricrepresentation variables with respect to a shape distributed on thechromaticity coordinate; estimating a color temperature from the inputcolor image by perceptive light source estimation; and selectinggeometric representation variables around the estimated colortemperature from the geometric representation variables and calculatinga final color temperature using the selected geometric representationvariables.
 9. The method of claim 2, wherein a saturation value isobtained by the following steps comprising: obtaining saturation of eachpixel in a HSV color space from an RGB value of a pixel in the image;and generating a value obtained by adding saturation of the pixels anddividing the added saturation by the number of pixels, as a saturationvalue.
 10. The method of claim 9, wherein the saturation of the pixel isdetermined by the following steps comprising: obtaining maximum andminimum values of the RGB value of the pixel; and when the maximum valueis equal to 0, setting the saturation of a corresponding pixel to 0, andwhen the maximum value is not equal to 0, setting a value obtained bydividing a difference between the maximum value and the minimum value bythe maximum value, as the saturation of a corresponding pixel.
 11. Themethod of claim 2, wherein a brightness value is determined by thefollowing steps comprising: obtaining luminance Y of each pixel in aYCbCr color space from an RGB value of a pixel in the image; andgenerating a value obtained by adding luminance of the pixels anddividing the added luminance by the number of pixels, as a brightnessvalue.
 12. The method of claim 11, wherein the luminance Y of the pixelis determined by Y=0.299×R+0.587×G+0.114×B.
 13. The method of claim 2,wherein a contrast value CV is, when Yx is luminance of each pixel inthe image and NumberofPixels is the number of pixels in the image,determined using equation:${C\; V} = \sqrt{\frac{\lbrack {\sum\limits_{x \in {({pixels})}}\; ( {Y_{x} - {BV}} )^{2}} \rbrack}{NumberOfPixels}}$14. The method of claim 2, wherein step (a) further comprising, when{preference value, reference value} exists before {preference value,reference value} in step (a) is generated, comparing the pair{preference value, reference value} generated in step (a) with anexisting pair {preference value, reference value} and updating the pair{preference value, reference value}, wherein the updating is, withrespect to one preference value, when the reference value generated instep (a) is compared with the existing reference value and is the sameas or similar to the existing reference value, removing the existingreference value.
 15. The method of claim 7, wherein step (b) furthercomprising, when {preference value, reference value} exists before{preference value, reference value} in step (b) is generated, comparingthe pair {preference value, reference value} generated in step (b) withan existing pair {preference value, reference value} and updating thepair {preference value, reference value}, wherein the updating is, withrespect to one preference value, when the reference value generated instep (b) is compared with the existing reference value and is the sameas or similar to the existing reference value, removing the existingreference value.
 16. The method of claim 14, wherein the updating is,when quantization levels of the two reference values are different,converting a value of high level into a value of low level and comparingwith each other, and when image contents identifiers are added to thecharacteristic value pairs, even though the two reference values are thesame as or similar to each other, if the image contents identifiers aredifferent, without removing the existing reference value.
 17. The methodof claim 2, wherein the number of the feature blocks is four, and eachof the feature blocks corresponds to the four characteristic values. 18.The method of claim 2, wherein the block header of the feature blockrepresents color temperature if the value of the feature identifier is‘0’, brightness if the value thereof is ‘1’, contrast if the valuethereof is ‘2’, and saturation if the value thereof is ‘3’.
 19. Themethod of claim 2, wherein the block header of the feature block furthercomprises a number-of-descriptors value indicating the number of featuredescriptors contained in the feature block.
 20. The method of claim 2,wherein the feature descriptor further comprises: a Bin numberindicating a quantization level of the characteristic value; a contentsID flag indicating the presence of an image contents identifier; and acontents identifier if the image contents identifier exists.
 21. Anapparatus for generating user preference data regarding a colorcharacteristic of an image, when an image converted to have a colorcharacteristic that a user prefers with respect to predeterminedreference image is referred to as a preference image, a colorcharacteristic value of the preference image is referred to as apreference value and a color characteristic value of the reference imageis referred to as a preference value and a color characteristics valueof the reference image is referred to as a reference value, theapparatus comprising: a color characteristic calculating unit, whichobtains an image color characteristic value of the preference image andthe reference image, and generates {preference value, reference value}which corresponds to a pair of the preference value and the referencevalue; and a meta-data generating unit, which generates the pair{preference value, reference value} generated in the colorcharacteristic calculating unit as preference meta-data having at leastone feature block, wherein the feature block comprises: a block headerincluding a feature identifier corresponding to information identifyinga color characteristic; and at least one feature descriptor includingthe preference value and the reference value.
 22. The apparatus of claim21, wherein the color characteristic is at least one of colortemperature, brightness, contrast, and saturation.
 23. The apparatus ofclaim 21, further comprising a first sample image obtaining unit, whichsets an image that the user has selected from a plurality of imageshaving different color characteristic values with respect to apredetermined image, sets an original image with respect to thepreference image as a reference image, generates {preference image,reference image} which corresponds to a pair of the preference image andthe reference image, and outputs the pair to the color characteristiccalculating unit.
 24. The apparatus of claim 21, further comprising asecond sample image obtaining unit, which, when a unit for controlling acolor characteristic of an image is installed in an image displaydevice, sets an image of which color characteristic is adjusted by auser using the unit for controlling a color characteristic, as apreference image, sets an original image of which color characteristicis not adjusted by the user, as a reference image, generates {preferenceimage, reference image} which corresponds to a pair of the preferenceimage and the reference image, and outputs the pair to the colorcharacteristic calculating unit.
 25. The apparatus of claim 23, whereinthe generating {preference image, reference image} is, when thereference image has a contents identifier, generating {preference image,reference image, contents identifier} which corresponds to a combinationof the preference image, the reference image, and contents identifierinformation.
 26. The apparatus of claim 25, wherein the colorcharacteristic calculating unit, when the reference image has a contentsidentifier, further comprises a contents identifier in the pair{preference value, reference value} and generates a combination{preference value, reference value, contents identifier}.
 27. Theapparatus of claim 22, wherein the color characteristic calculating unitcomprises a color temperature value calculating portion, which obtains acolor temperature value, and wherein the color temperature valuecalculating portion comprises: a highlight detecting part, whichextracts a highlight region from an input color image; a highlightvariable calculating part, which projects the highlight region on achromaticity coordinate and calculates geometric representationvariables with respect to a shape distributed on the chromaticitycoordinate; a color temperature estimating part, which estimates a colortemperature from the input color image by perceptive light sourceestimation; and a color temperature calculating part, which selectsgeometric representation variables around the estimated colortemperature from the geometric representation variables and calculates afinal color temperature using the selected geometric representationvariables.
 28. The apparatus of claim 22, wherein the colorcharacteristic calculating unit comprises a saturation value calculatingportion, which obtains saturation of each pixel in a HSV color spacefrom an RGB value of a pixel in the image and generates a value obtainedby adding saturation of the pixels and dividing the added saturation bythe number of pixels, as a saturation value, and wherein the saturationof the pixel is determined by the following steps comprising: obtainingmaximum and minimum values of the RGB value of the pixel; and when themaximum value is equal to 0, setting the saturation of a correspondingpixel to 0, and when the maximum value is not equal to 0, setting avalue obtained by dividing a difference between the maximum value andthe minimum value by the maximum value, as the saturation of acorresponding pixel.
 29. The apparatus of claim 22, wherein the colorcharacteristic calculating unit comprises a brightness value calculatingportion, which obtains luminance Y of each pixel in a YCbCr color spacefrom an RGB value of a pixel in the image and generates a value obtainedby adding luminance of the pixels and dividing the added luminance bythe number of pixels, as a brightness value, and wherein the luminance Yof the pixel is determined by Y=0.299×R+0.587×G+0.114×B.
 30. Theapparatus of claim 22, wherein the color characteristic calculating unitcomprises a contrast value calculating portion, which, when Yx isluminance of each pixel in the image and NumberofPixels is the number ofpixels in the image, calculates a contrast value determined usingequation 3:
 31. The apparatus of claim 22, further comprising ameta-data updating unit, which compares the pair {preference value,reference value} generated in the color characteristic calculating unitwith an existing pair {preference value, reference value}, updates thepair {preference value, reference value}, and outputs the pair to themeta-data generating unit, wherein the updating is, with respect to onepreference value, when the reference value generated in step (b) iscompared with the existing reference value and is the same as or similarto the existing reference value, removing the existing reference value,and the updating is, when quantization levels of the two referencevalues are different, converting a value of high level into a value oflow level and comparing with each other, and when image contentsidentifiers are added to the characteristic value pairs, even though thetwo reference values are the same as or similar to each other, if theimage contents identifiers are different, without removing the existingreference value.
 32. The apparatus of claim 22, wherein the block headerof the feature block further comprises a number-of-descriptors valueindicating the number of feature descriptors contained in the featureblock.
 33. An image preference data recording medium on which, when animage converted to have a color characteristic that a user prefers withrespect to a predetermined image is referred to as a preference image,the predetermined image is referred to as a reference image, a colorcharacteristic value of the preference image is referred to as apreference value, and a color characteristic value of the referenceimage is referred to as a reference value, preference meta-data havingat least one feature block, the feature block comprising a block headerincluding a feature identifier corresponding to information identifyinga color characteristic and at least one feature descriptor including thepreference value and the reference value is recorded.
 34. The recordingmedium of claim 33, wherein the block header of the feature blockfurther comprises a number-of-descriptors value indicating the number offeature descriptors contained in the feature block, and wherein thefeature descriptor further comprises: a Bin number indicating aquantization level of the characteristic value; a contents ID flagindicating the presence of an image contents identifier; and a contentsidentifier if the image contents identifier exists.
 35. A computerreadable recording medium on which the invention of claim 1 is recordedas an executable program code.